A novel porous cocoon-like reduced graphene oxide (rGO) with high porosity and low density was fabricated by a simple and green reduction reaction using ascorbic acid as the reductant in combination with a freeze-drying process without annealing. The bulk density of porous cocoon-like rGO is only 28.49 mg/cm3, and the porosity reaches 94.57%. The reaction times have an important influence on the formation of porous cocoon-like rGO and the reduction degree of rGO. The porous cocoon-like rGO exhibits an excellent microwave-absorbing property with a low mass filling ratio of 7.0 wt %; its minimum reflection loss (RL) is −29.05 dB at 15.96 GHz with a sample thickness of 2.0 mm and the effective absorption bandwidth (RL < −10 dB) is 5.27 GHz. The microwave-absorbing property of porous cocoon-like rGO is much better than that of GO and other porous rGO. The in-depth analyses of the reduction degree, porosity, and microwave-absorbing performance illustrate that the microwave-absorbing performance of rGO is significantly related to the reduction degree and porosity. In addition, the synthetic route for porous cocoon-like rGO is simple, has low energy consumption, and is environmentally friendly. Our work demonstrates that the porous cocoon-like rGO is a promising lightweight microwave absorber with high performance.

The terephthalate‐intercalated LDHs (TA‐LDHs) are used to improve the barrier properties of poly(ethylene terephthalate) (PET) for their application in liquid food packaging. First, TA‐LDHs were synthesized from freshly prepared metal hydroxides. PET/LDH nanocomposites were then prepared by a masterbatch process. The structures and morphologies of TA‐LDHs and PET/LDH nanocomposites were characterized using X‐ray diffractometer, transmission electronic microscopy, and scanning electron microscope. The mechanical performances and the oxygen permeability of the PET/LDH composites were measured using a precision universal tester and differential pressure gas permeameter, respectively. The influence of TA‐LDH content on their structures and properties was studied. PET/LDH nanocomposites with 1 and 2 wt% of TA‐LDHs are partially exfoliated nanocomposites, while PET/LDH with 5 wt% of TA‐LDHs is an intercalated nanocomposite. The PET/LDH nanocomposites prepared by a masterbatch process show better mechanical properties and gas barrier properties. PET/LDHs‐m2 with 2 wt% of TA‐LDHs could offer up to a 29.4% improvement in tensile strength over PET and the Young's modulus is increased by 38.9%. The O2 permeation of PET/LDHs‐m2 with 2 wt% of TA‐LDHs is decreased by 46.2%. POLYM. ENG. SCI., 59:E366–E371, 2019. © 2019 Society of Plastics Engineers

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Polyamide 12 (PA12)-coated SiO 2 composite powders were prepared by a dissolution-precipitation method using a mixture of methanol and ethanol as the solvent. The sizes and morphologies of the as-obtained composite powders were determined and observed using a laser particle size analyzer and a scanning electron microscope. The effects of SiO 2 content on the sizes and the thermal properties of PA12@SiO 2 composite powders were studied. The results show that the introduction of SiO 2 decreases the size of the composite powders. With increasing content of SiO 2 to 9.1 wt%, the d (0.5) of the PA12 powders decreases from 94.2 to 56.2 lm. SiO 2 promotes the heterogeneous nucleation of PA12, and the size of the composite powders can be tuned by changing the amount of the SiO 2 . In addition, SiO 2 particles increase the melting and crystallization temperatures and the crystallization rate of PA12. POLYM. COMPOS., 00:000-000, ety of Plastics Engineers POLYMER COMPOSITES-2019 FIG. 3. SEM micrographs and size distributions of PA12@SiO 2 composite powders with different SiO 2 content: (a) 2.6 wt%; (b) 4.3 wt%; (c) 5.4 wt%; (d) 7.4 wt%; (e) 9.1 wt%. FIG. 6. DSC scans of the heating curves and cooling curves of PA12 and PA12@SiO2 composite powders with 7.4 wt% of SiO 2 .